The importance of links and their impact on search engine rankings and traffic has motivated many to seek quick fixes and automated solutions. These approaches tend to focus purely on building the maximum number of links with the minimum amount of effort, with little regard for relevancy, usefulness or ethics. This has resulted in an explosion of link farms, reciprocal link spam and many other attempts to build links quickly at minimal cost. Obviously, the search engines are not too happy about these techniques, as they are often used to make low-value sites look popular and respected when in fact they have little to offer Internet users. Search engines have gone out of their way to minimize the impact of these approaches.
I would suggest that a more sustainable and effective approach is to focus on marketing activities that generate links as a by-product of the core activity. Below I discuss some of the more important marketing activities that build links to your site.
Content is King. This phrase is a bit like "exercise more, eat less"--we have all heard it a thousand times, but this only makes it more true. The most effective link-building strategy of all is to simply add valuable content to your Web site. Other sites will link to your content if they believe their own visitors will find it useful. Popular content includes presentations, white papers, newsletters and the ever-popular blog. With blogs, it's important that you use a system that allows you to host them under your own domain name, so the links to the blog go to your domain name, not the blogging system. Another simple approach is to provide a "Link to this article" system that automatically produces linking code for the article in question.
"Powered By". If you provide an online service or tool, then the good old-fashioned "powered by" link is a must. Search engines have started to reduce the relevance of these types of link, as large online service providers can easily generate thousands of identical links using this technique. However, the approach still works and is still valid--both as a link-building and a brand-building exercise.
Awards. If you are a respected industry commentator, then presenting awards to sites can be an effective way to reinforce your brand position and also build quality links.
Affiliate Marketing. Affiliate marketing in itself is a very effective tactic, but as Amazon, with its million-plus links, has demonstrated, it is also a great link builder. As with the blog and RSS approaches, it is essential that the links used by affiliates point directly to your domain name and not to the affiliate system you happen to be using (most affiliate systems have a "direct linking" option).
In summary, don't kill yourself obsessing over links for links' sake; implement a diverse online marketing plan that offers valuable content; work with other sites; and your links will take care of themselves.